Siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include low glass transition temperature, thermal and oxidative stability, resistance to ultraviolet radiation, low surface energy and hydrophobicity, high permeability to many gases, and biocompatibility. The siloxane polymers, however, often lack tensile strength.
The low tensile strength of the siloxane polymers can be improved by forming block copolymers. Some block copolymers contain a “soft” siloxane (e.g., polydiorganosiloxane) polymeric block or segment and any of a variety of “hard” blocks or segments. Examples include polydiorganosiloxane polyureas and polydiorganosiloxane polyoxamide copolymers. These polymeric materials can be used, for example, to prepare adhesive compositions and various types of polymeric films.